Converter In Continuous Conduction Mode Research Articles

A Novel Buck–Boost Converter With Low Electric Stress on Components

In this paper, a novel buck–boost converter with low electric stress on components and negative output voltage is proposed. The operational principle, steady-state analysis, and small-signal modeling of the proposed buck–boost converter in continuous conduction mode are presented. Comparisons among another five buck–boost converters and the proposed buck–boost converter are presented. It is found that the proposed converter's voltage gain is smaller than the other converters’ in step-down mode. Also, based upon the comparisons among the same kind and same number of components, the voltage and current stresses on the power switch of the proposed buck–boost converter are less than or equal to those of the comparative converters, and the voltage stress on the charge pump capacitor and the switching device power rating of the proposed buck–boost converter are always lower than those of other comparative converters. The efficiency of the proposed buck–boost converter is highest among those converters having the same number of elements. These advantages make component selection for the proposed converter much easier, and it can be used directly in applications needing a negative voltage source. Finally, simulation results and circuit experiments are given for validating the effectiveness of the proposed buck–boost converter.

A Digital Control Scheme for PSR Flyback Converter in CCM and DCM

Due to the simple structure and low cost, the primary-side-regulation (PSR) flyback converter is widely used in small power applications. As the output voltage is sampled from auxiliary winding in PSR flyback converter, some sampling error exists, especially when continuous conduction mode (CCM) is introduced for higher power. To improve the constant voltage accuracy, a novel digital controlled sampling strategy is proposed. This scheme uses a digital ramp sampling method to sample output voltage in both discontinuous conduction mode (DCM) and CCM, and proposes a voltage adjustment strategy to adjust sampling errors in CCM without weakening the stability in the load-switch process. Finally, the experimental results validate the presented scheme and show that the output voltage error is less than 0.6% in a 20-V, 5-A PSR flyback prototype.

Analysis, Design and Control of an Integrated Three-Level Buck Converter under DCM Operation

A three-level buck (TLB) converter has the characteristics of higher voltage conversion efficiency, lower inductor current ripples, output voltage ripples and voltage stresses on switches when compared with the buck converters in continuous conduction mode (CCM). With a TLB converter integrated on a chip, we cannot avoid its discontinuous conduction mode (DCM) operation due to a smaller inductance and load variation. In this paper, we’ll present and discuss the analysis, design and control of a TLB converter under DCM operation, implemented in a 65[Formula: see text]nm CMOS process. Transistor level simulation results show that when the TLB converter operates at 100[Formula: see text]MHz with a 5[Formula: see text]nH on-chip inductor, a 10[Formula: see text]nF output capacitor and a 10[Formula: see text]nF flying capacitor, it can achieve an output conversion range of 0.7–1.2[Formula: see text]V from a 2.4[Formula: see text]V input supply, with a peak efficiency of 81.5%@120[Formula: see text]mW. The output load transient response is 100[Formula: see text]mV with 101[Formula: see text]ns for undershoot, and 86[Formula: see text]mV with 110[Formula: see text]ns for overshoot when [Formula: see text]–100[Formula: see text]mA. The maximum output voltage ripple is less than 19[Formula: see text]mV.

Mathematical modelling and analysis of voltage super-lift power dc-dc converter for enhanced dynamic characteristics in CCM

PurposeThe purpose of this paper is to propose a mathematical model for voltage super-lift dc-dc power converter in continuous conduction mode (CCM). Using the presented mathematical model, the analysis of dynamics of power stage for voltage super-lift dc-dc power converter can be performed.Design/methodology/approachThe proposed method is based on the average state space model using the state equations of the dc-dc power converter. In the proposed method, the converter is represented as a set of differential equations derived for each switching state of the power switch in terms of inductor current and capacitor voltage. The proposed method describes the dynamic behaviour of the system. The controller is designed to meet performance requirement of the system such as to maintain the dynamics such as stability, steady-state accuracy and the speed of response of the system. Using the obtained model, the analysis of dynamic response of the voltage super-lift dc-dc power converter can be performed.FindingsThe converter is modelled and verified using conventional circuit analysis method employing state-space averaging technique, and their corresponding transfer function is also derived. The dynamics of the converter is investigated using frequency response characteristics obtained using MATLAB programming environment. In addition, to improve the stability of the converter, proportional-integral controller is designed using Ziegler–Nichols tuning rules, and the effect of the compensator in the plant is also investigated.Originality/valueThe proposed method can be used for analysing the dynamics of power stage for voltage super-lift DC-DC power converter.

Analysis, modeling, and implementation of a new transformerless semi‐quadratic Buck–boost DC/DC converter

SummaryThis paper presents a novel transformerless semi‐quadratic buck‐boost converter (SQBuBoC). In the proposed SQBuBoC, two power switches with simultaneous operation are used and a higher step‐up/step‐down voltage conversion ratio is achieved compared with the traditional buck‐boost, Cuk, single‐ended primary‐inductor converter, and Zeta converters. The positive polarity of the output voltage, along with low ripple continuous input current and common ground between the source and the output voltages, are some features that make the suggested topology more suitable for many applications with wide range of output voltage such as photovoltaic systems. Moreover, the total voltage stress across the power switches in this converter is lower than the cascade boost, and the traditional buck‐boost converters led to power MOSFETs selection with lower drain‐source ON resistance (Rds) and efficiency improvement. All the steady‐state analysis and comparisons in continuous conduction mode (CCM) are discussed in details. In addition, to study the low frequency behavior of the SQBuBoC by means of the state‐space averaging technique, the small and large signal models of this converter in CCM are presented. Finally, the SQBuBoC analysis is justified using experimental results of a 50 W step‐up 25 V to 120 V and a 28 W step‐down 25 V to 14 V laboratory prototypes.

Unified Second-Stage LC Filter Applied in the Three-State Switching Cell Buck–Boost Converter: Static and Dynamic Analysis and Experimentation

This paper presents a unified second-stage LC filter applied in the three-state switching cell buck-boost converter, which provides current and voltage with low ripple and low noise. The unified second-stage filter promotes a reduction in the number of devices while maintaining the filtering performance of the converter, with second-stage LC filters at the input and at the output. Moreover, the unified filter, when associated with a three-state switching cell buck- boost converter, allows a size reduction of filter devices, especially for designs with duty cycle range around 1/2. Furthermore, the unified filter arrangement provides nondissipative clamping of switching devices and reduce the system order when compared to the converter with second-stage LC filters. In this paper, the static and dynamic characteristics of the proposed converter in continuous conduction mode (CCM) are reported. Experimental data were obtained from a laboratory prototype with an input range of 32~72 V, constant output of 48 V, a load of 150 W, and switching frequency of 45 kHz. The measured efficiency for the rated load was 97% for maximum input voltage. A comparison of the size and performance of the proposed filter with the topology that uses second-stage LCfilters at the input and at the output is also presented.

Soft Computing Technique of Bridgeless SEPIC Converter for PMBLDC Motor Drive

A novel speed controller for the three-phase Brushless DC (BLDC) Motor Drive is proposed using a closed-loop AC-DC Bridgeless SEPIC Converter in continuous Conduction mode. This design proposes a single stage AC-DC converter with ON and OFF state equivalent circuits for 400W, 48V at 2450 rpm PMBLDC motor drive. The Fuzzy based voltage and current controlling method is proposed in this design. The voltage controlling method is used to control the speed for BLDC motor and the current controlling method is used to improve the power factor in AC supply. The speed of BLDC motor is observed with voltage disturbance and the constant motor speed is maintained. The proposed control method on SEPIC converter fed PMBLDC motor drive is modeled by Simulink/Matlab.

Digital Average Voltage/Digital Average Current Predictive Control for Switching DC–DC Converters

In this paper, the digital average voltage/digital average current (DAV/DAC) predictive control for switching dc–dc converter is proposed. The advantages of the proposed predictive control technique include no subharmonic oscillation in the full range of duty cycle, wide stability range, fast load transient response, and realization of overcurrent protection. Taking buck converter in continuous conduction mode as an example, the algorithm of DAV/DAC predictive control is analyzed in detail. The sampled-data modeling is performed to explore the stability of DAV/DAC predictive control, by which the stability boundary is obtained. The z -domain small-signal model of DAV/DAC predictive control is also derived to analyze the load transient performance. The analysis results prove that DAV/DAC predictive control is the combined control of the existed DAV predictive control and DAC predictive control in the previous publications. The stability boundary and transient performances of DAV/DAC controlled buck converter are influenced by the weighted factors of inductor current and output voltage, and a simple design oriented reference about the weighted factors is given in this paper. Finally, the theoretical analysis is verified by simulations and experiments.

A non‐isolated high step‐up DC‐DC converter with integrated 3 winding coupled inductor and reduced switch voltage stress

SummaryIn this paper, a non‐isolated high step‐up dc‐dc converter based on coupled inductor is proposed. The proposed converter can be used in renewable energy applications. In suggested converter, the high voltage is achieved using 3‐winding coupled inductor, which leads to low voltage rate of the switch. A clamp circuit is used to recycle the leakage inductance energy. Also, the clamp circuit prevents the creation of voltage spikes on semiconductor devices and causes the voltage stress of elements are limited to less than the output voltage. The presented theoretical analyses show that the operation of suggested converter in continuous conduction mode needs to small magnetic inductor. Therefore, the size of coupled inductor's core is reduced, and so the size and cost of presented converter will be decreased. Analysis of the proposed converter is provided with laboratory results to verify its performance.

Fractional-Order Modeling and Simulation of Magnetic Coupled Boost Converter in Continuous Conduction Mode

By using fractional-order calculus theory and considering the condition that capacitor and inductor are naturally fractional, we construct the fractional mathematical model of the magnetic coupled boost converter with tapped-inductor in the operation of continuous conduction mode (CCM). The fractional state average model of the magnetic coupled boost converter in CCM operation is built by exploiting state average modeling method. In these models, the effects of coupling factor, which is viewed as one generally, are directly pointed out. The DC component, the AC component, the transfer functions and the requirements of the magnetic coupled boost converter in CCM operation are obtained and investigated on the basis of the state averaged model as well as its fractional mathematical model. Using the modified Oustaloup’s method for filter approximation algorithm, the derived models are simulated and compared using Matlab/Simulink. In order to further verify the fractional model, circuit simulation is implemented. Furthermore, the differences between the fractional-order mathematical models and the corresponding integer-order mathematical models are researched. Results of the model and circuit simulations validate the effectiveness of theoretical analysis.

Small-Signal Model of Flyback Converter in Continuous-Conduction Mode With Peak-Current Control at Variable Switching Frequency

Flyback converter is widely used in low-power adaptor applications. To achieve high efficiency for the entire load range of operations, the variable-frequency peak-current-mode (VFPCM) control is often used in the flyback converter to reduce switching frequency at light load. Since there is no small-signal model being developed for the VFPCM control to overcome the unstable problem in a wide range of operations, the present study proposes a novel, accurate small-signal model for VFPCM control operated in continuous-conduction mode. Control behavior and design are analyzed and compared with constant-frequency peak-current-mode control to give engineers insight. A control IC and a flyback converter are built for the experimental validation of the proposed model. Experimental and simulation results verify the proposed model.

Unified modelling and dynamical analysis of current‐mode controlled single‐inductor dual‐output switching converter with ramp compensation

Current-mode controlled single-inductor dual-output (SIDO) switching converters have three borders in wide-range parameter variations. Based on the slopes of inductor current during the power switches being turn-on or turn-off, a unified discrete-mapping model of current-mode controlled SIDO switching converters with ramp compensation is established in this study, which can be applied to three basic SIDO switching converters, i.e. buck type, boost type, and buck-boost type. Only six parameters appear in this model after non-dimensional analysis, from which the dynamical behaviours of SIDO switching converters in continuous conduction mode (CCM) and discontinuous conduction mode (DCM) can be effectively illustrated. The effect of ramp compensation is analysed in detail. By utilising the proposed unified model, two transition conditions and boundary equations of the converter are derived, where its operation state transits from stable period-1 to instability and operation mode shifts from CCM to DCM. The operation region with varied circuit parameters can be estimated and divided by the parameter-space map, which is significant for the design of circuit parameters and stability. Finally, taking a current-mode controlled SIDO boost converter as an example, its experimental results are carried out to validate the theoretic analysis and the non-dimensional unified model.

Order Reduction of Linear Dynamic Systems by Improved Routh Approximation Method

ABSTRACTIn this paper, a new simplified Routh approximation technique is proposed for the model order reduction (MOR) of large scale linear time-invariant systems. In reduced order modeling, the Routh approximation technique described in the literature is based on the alpha and beta parameters. This paper presents a new simplified Routh approximation technique for the MOR involving only alpha parameters to make the proposed technique simple. In this technique, the denominator polynomial of the lower order system is obtained by the Routh approximation technique and the numerator polynomial is computed by a simple mathematical algorithm as discussed in the proposed scenario. The additional advantage of the proposed method is that it always gives a stable reduced model if the original higher-order system is stable. To illustrate the proposed method, the fourth-order DC–DC converter model is reduced to its second-order reduced model. The modeling of DC–DC converter in continuous conduction mode is also developed and whose final output is a complete linear circuit model. In order to check the effectiveness and accuracy competitive to other popular and recent techniques in the literature, the proposed method has been applied on various standard numerical examples.

A Class of Quasi-Cuk DC/DC Converters: Steady-State Analysis and Design

In this paper, new topologies for quasi-Cuk converter are proposed. The proposed converters with different voltage and current transfer ratio and reduced voltage stress on capacitor can be employed in distributed generation (DG) systems. In this paper, steady-state analysis of two proposed quasi-Cuk converters in continuous conduction mode (CCM) and discontinuous conduction mode (DCM) is presented. Then, besides values designing of used elements, maximum and minimum values of their current and voltage are calculated. Moreover, critical inductances between CCM and DCM for the proposed converters are calculated. Unique features of the proposed converters are different transfer ratio without employing additional elements compared to the conventional Cuk converter. Comparison of the proposed converters with conventional converter in terms of voltage transfer ratio, voltage stress on capacitor, and voltage stress on switch demonstrates advantages of the proposed converters. Finally, experimental results to verify the accuracy of the proposed converters in different operating modes are presented.

Sensorless control of wind SRG in dc microgrid application

This paper presents an innovative and effective control strategy of Switched Reluctance Generator (SRG), operating with Vujicic-Calasan PCT1 power converter in continuous-conduction mode (CCM), for a wind energy conversion system (WECS) employed in DC microgrids. The Vujicic-Calasan PCT1 power converter, whose validity in this paper is additionally confirmed through simulations and experimental results, is based on diode bridge rectifiers and does not contain switch components. Namely, it requires four diodes and one inductance filter per machine phases as well as one excitation voltage source. By regulating the dc excitation voltage the output power of SRG can be easily controlled. A procedure for determination of the optimal excitation voltage as a function of rotor speed, that provides maximal output power for defined RMS phase current and voltage is proposed. Moreover, the obtained optimal dependences are mathematically described to be used for control of SRG in WECS. In the simulations performed to study the proposed control strategy, a realistic wind profile is used, while the turbine operation with and without pitch controller is considered. Simulations results provided for the WECS confirm that the proposed control strategy ensures system stability and fast maximal power point tracking.

Exponentially Stable Lyapunov-Function-Based Controller for a Flyback CCM Converter

In this paper, we propose a Lyapunov-function-based controller for the flyback converter operating in the continuous conduction mode (CCM). The controller consists of a duty-ratio feedforward control unit and a Lyapunov-function-based feedback control unit. The duty-ratio feedforward signal is used to reduce the burden from the Lyapunov feedback controller. The control system guarantees global exponential stability of the closed-loop system and, hence, offers fast transient response under large-signal perturbations. In constructing the controller, we use the average model of the flyback CCM converter taking the parasitic components into account. Numerical simulations confirmed its superior performance, and experimental tests validated the proposed control approach.

Analysis of Pulse Train Controlled PCCM Boost Converter With Low Frequency Oscillation Suppression

For pulse train (PT) controlled switching converter, when it operates in continuous conduction mode (CCM) and discontinuous conduction mode (DCM), there exist disadvantages of low frequency oscillation and narrow load range, respectively. To avoid these disadvantages of PT controlled switching converter in CCM and DCM, a PT controlled boost converter operating in pseudo continuous conduction mode (PCCM) is taken as the research object in this paper, its working principle has been analyzed in detail. Based on the analysis of output voltage ripple during one switching cycle, the combination of high- and low-power control pulses in a repetition cycle is analyzed and the expression of output voltage ripple is derived for different load conditions. Finally, simulation and experiment are performed to verify the correctness of the control pulse combinations and the output voltage ripple analysis. Results show that compared with DCM and CCM boost converters, the PT controlled PCCM boost converter not only has wider load range, but also can suppress low frequency oscillation.

Analysis and design of single phase power factor correction with DC–DC SEPIC Converter for fast dynamic response using genetic algorithm optimised PI controller

This study presents the analysis and design of a single phase power factor correction (PFC) scheme using a DC–DC single ended primary inductance converter with genetic algorithm (GA)-tuned proportional integral (PI) controllers. A systematic off-line design approach using GA for optimising the parameters of the PI controller is proposed and the performance is compared with the conventional Z–N tuned PI controller. The steady-state and transient responses of the converter subjected to a change in the load, set point and line variations are investigated. The performance analysis of the proposed converter in continuous conduction mode is made for the above-mentioned methods using Matlab/Simulink-based simulation studies and experimental set up. Results reveal that the GA-tuned PI controller yields superior performance to the Z–N tuned PI controller in terms of power factor, percentage total harmonic distortion, regulated output voltage for the variations in line, load and efficient tracking of output voltage for a change in the reference voltage.

Sampled-data modeling and dynamical effect of output-capacitor time-constant for valley voltage-mode controlled buck-boost converter**Project supported by the National Natural Science Foundation of China (Grant Nos. 61371033 and 51407054), the Foundation for the Author of National Excellent Doctoral Dissertation of China (Grant No. 201442), and the Fundamental Research Funds for the Central Universities of China (Grant No. 2682016CX035).

By analyzing the output voltage ripple of a buck-boost converter with large equivalent series resistance (ESR) of output capacitor, one valley voltage-mode controller for buck-boost converter is proposed. Considering the fact that the increasing and decreasing slopes of the inductor current are assumed to be constant during each switching cycle, an especial sampled-data model of valley voltage-mode controlled buck-boost converter is established. Based on this model, the dynamical effect of an output-capacitor time-constant on the valley voltage-mode controlled buck-boost converter is revealed and analyzed via the bifurcation diagrams, the movements of eigenvalues, the Lyapunov exponent spectra, the boundary equations, and the operating-state regions. It is found that with gradual reduction of output-capacitor time-constant, the buck-boost converter in continuous conduction mode (CCM) shows the evolutive dynamic behavior from period-1 to period-2, period-4, period-8, chaos, and invalid state. The stability boundary and the invalidated boundary are derived theoretically by stability analysis, where the stable state of valley voltage-mode controlled buck-boost converter can enter into an unstable state, and the converter can shift from the operation region to a forbidden region. These results verified by time-domain waveforms and phase portraits of both simulation and experiment indicate that the sampled-data model is correct and the time constant of the output capacitor is a critical factor for valley voltage-mode controlled buck-boost converter, which has a significant effect on the dynamics as well as control stability.

SRG converter topologies for continuous conduction operation: a comparative evaluation

In this study, the comparative evaluation of the asymmetric, Derishzadeh and Vujicic-Calasan power electronic converters for switched reluctance generator (SRG) operation in continuous conduction mode (CCM) is performed. The output SRG drive characteristics and converter complexity are chosen as criteria for comparative evaluation. It is shown that the optimal control of Vujicic-Calasan converters enables obtaining the same power as the optimal control of classic converter in CCM as well as optimal control of Derishzadeh converter. However, the Vujicic-Calasan converters are simpler and can be easily controlled since it does not contain switch components and does not require position sensor information. The additional experimental results, which confirm effectiveness of SRG operation with Vujicic-Calasan converters, are also presented.